چکیده انگلیسی

From the perspective that disgust is a core feature of spider phobia, we investigated whether the treatment efficacy could be improved by adding a counterconditioning procedure. Women with a clinically diagnosed spider phobia (N=34) were randomly assigned to the regular one-session exposure condition (EXP) or to the exposure with counterconditioning condition (CC). In the CC-condition tasty food-items were used during the regular exposure exercises and the participants' favourite music was played. Both treatment conditions appeared very effective in reducing avoidance behaviour and self-reported fear of spiders, strongly attenuated the disgusting properties of spiders and altered the affective evaluations in a positive direction. CC was not more effective in altering the affective valence of spiders than EXP and was not superior with respect to the long term treatment efficacy at 1 year follow up. Apparently, regular exposure treatment is already quite effective in altering the affective-evaluative component of spider phobia and it remains to be seen whether it is possible to further improve treatment outcome by means of procedures which are specifically designed to reduce the spiders' negative affective valence.

مقدمه انگلیسی

There is increasing evidence that disgust and fear of contamination somehow underlie spider phobia. Indirect support for this position is provided by a series of studies demonstrating that common spider fear correlates with disgust sensitivity as indexed by both the Disgust Questionnaire (DQ; Rozin, Fallon & Mandell, 1984), a questionnaire which is mainly concerned with food contamination by animal products (Davey, 1992, de Jong and Merckelbach, 1998 and Mulkens et al., 1996), as well as by the Disgust Scale (DS; Haidt, McCauley & Rozin, 1994), which is a broader index of disgust sensitivity covering seven domains of disgust elicitors such as body products, animals and body envelope violations (de Jong and Merckelbach, 1998 and Tolin et al., 1997).
In line with this, women as well as children with a clinically diagnosed spider phobia were found to have higher levels of disgust sensitivity than nonphobic controls (de Jong et al., 1997, Mulkens et al., 1996 and Thorpe and Salkovskis, 1998). The higher levels of disgust sensitivity in the phobic groups could not be attributed to higher levels of trait anxiety or neuroticism (de Jong et al., 1997 and Mulkens et al., 1996). Furthermore, the repeated finding that DQ scores of spider phobics remain unaffected after successful treatment (de Jong et al., 1997 and Merckelbach et al., 1993) clearly refutes the suggestion that high levels of disgust sensitivity as indexed by the DQ are a mere epiphenomenon of phobic fear (e.g. Thorpe & Salkovskis, 1998).
More direct evidence for the relationship between disgust and spider phobia was obtained by Mulkens and colleagues who showed that for spider phobic individuals, spiders share the crucial feature of all disgusting objects, namely that they can render perfectly good food-items inedible by brief contact, even when there is no detectable trace of the offensive item (e.g. Rozin & Fallon, 1987). During a behavioural test only 25% of a spider phobic group eventually ate (some of) a preferred cookie after it had been in short contact with a live spider versus 75% of the nonphobic women (Mulkens et al., 1996). Using an in vitro variant of this test, similar results were obtained in spider phobic children (de Jong et al., 1997).
Although it has been argued that this repugnance to eating the favourite food-item is fuelled by fear rather than disgust (e.g. Thorpe & Salkovskis, 1998), recent data render this possibility very unlikely. Note that if this would be the case, all phobic stimuli would have similar contaminating properties. Yet, in contrast to spider fearful participants, wasp fearful individuals (who are mainly afraid of being bitten) did not show a significant decline in their motivation to eat their favourite chocolate bar after it had been in brief contact with their phobic object, although the fear levels of both groups were virtually identical (Andrea, 1996). Clearly, these findings refute the idea that the contaminating properties of spiders are merely due to their fear evoking properties.
The idea that disgust plays an important role in spider phobia is further substantiated by the finding that the majority of spider phobic individuals reported that they consider their phobic stimulus (i.e. spider) as their most disgusting item (Thorpe & Salkovskis, 1998). Related, Tolin and colleagues (Tolin et al., 1997) demonstrated that the reactions of an analogue group of spider phobics to pictures of spiders were not restricted to fear but consisted of disgust as well. Note however, that during naturalistic confrontations with a spider, the threat of the spider's uncontrollable approach behaviour is likely to outstrip the typical symptoms of disgust such as feelings of dizziness, nausea and fainting. Germane to this possibility, it has been reported that in some individuals with blood-injection-injury phobia the typical (disgust related) vasovagal reaction first appeared after the fear of injections was strongly reduced (Öst, 1985 and Trijsburg et al., 1996). Following this, the strong (fear-related) sympathetical activity in spider phobics may outstrip the (disgust-related) increase of parasympathical activity and this may explain why the typical symptoms of disgust seldom occur when spider phobic individuals are confronted with a spider.
Perhaps, then, spider phobia can be best conceptualised as a fear of physical contact with a disgusting stimulus. For most disgusting stimuli the chances of unwanted and unexpected physical contact are negligible, as they are relatively immobile (e.g. faeces, blood, maggot) and/or do not tend to enter people's private territories (e.g. snail, worm). In contrast, spiders frequently cross the border of people's private living space and can move quickly. Therefore, the threat of unwanted physical contact seems much larger for spiders than for other disgusting objects or animals. Following this, the interaction of the spiders' disgusting properties and the threat of unwanted physical contact constitutes the fear of spiders. Germane to this, Davey (1993) found that disgust sensitivity considerably adds to individuals' fear ratings of a novel animal when it is modulated in an interactive fashion by beliefs about being physically contacted or attacked by the animal.
From the conceptualisation of spider phobia as an interaction of two orthogonal dimensions, there are two different starting points for the treatment of spider phobia. First, one can try to remove the intrinsically negative characteristics of spiders; second, one can learn the phobic individuals that the chance of unwanted physical contact is, in fact, extremely small. Clearly, the regular one-session in vivo exposure treatment (Öst, 1989a) takes hold of the latter dimension, as people learn during the exposure exercises that spiders, in fact, try to avoid physical contact and are highly predictable and well controllable. To the extent that individuals are encouraged to make prolonged physical contact with spiders, the regular in vivo exposure may also help to reduce the disgusting properties of spiders (cf. Rozin & Fallon, 1987). In line with this there is preliminary evidence indicating that the spiders' contaminating properties are attenuated after a one-session exposure in vivo (de Jong et al., 1997).
Although several studies have demonstrated that a 2.5 h one-session exposure is very effective in reducing fear and avoidance behaviour in spider phobia (e.g. Arntz and Lavy, 1993 and Öst et al., 1991), thus far the treatment of spider phobia is neither specifically tailored to reduce the disgust evoking status nor to alter the more general negative appreciation of spiders. Germane to this, Baeyens and colleagues wrote: “…, one would predict that the standard exposure based therapies are not able to alter this primary affective-evaluative component of the disorder (…). Clinical observation seems to confirm this prediction: after exposure therapy, the avoidance behaviour may be drastically reduced, but spiders remain nasty little animals. Maybe a counterconditioning experience provides the only way to change the negative evaluation of spiders towards more neutrality” (Baeyens, Eelen, van den Bergh & Crombez, 1989, p. 286); and “…For example, some animal phobias clearly better fit with the evaluative learning than with the signal-learning conceptualization (Matchett & Davey, 1991). Phenomenologically, the phobic object may be feared and/or disliked for itself rather than signalling the occurrence of a negative event; animal phobias often present themselves without detectable contingency awareness and are often extremely resistant to corrective verbal information concerning the stimulus contingencies; finally, exposure therapy (extinction procedure) is often not successful in altering the ‘intrinsic’ negative valence of the phobic object” (Baeyens, Eelen & van den Bergh, 1992, p. 134).
Neutralising the negative affective-evaluation of spiders and reducing the spiders disgusting properties may well further reduce individuals avoidance behaviours as well as their fear responses (cf. Rachman, 1981). In addition, it seems reasonable to argue that reducing the ‘intrinsic’ negative valence of spiders may help to prevent the return of phobic complaints. That is, unexpected future encounters with spiders or accidental physical contact is less likely to reinstate phobic fear if spiders are considered as neutral or even positive stimuli.
The present study was designed to investigate this issue in a clinical context. First, we explored whether and to what extent, a regular one-session exposure in vivo treatment already alters the affective valence of spiders as well as their disgusting properties. Second, we tested whether the treatment of spider phobia would be more effective with respect to measures of fear, valence and disgust if a counterconditioning procedure was added, which was specifically designed to reduce the spiders' disgusting properties as well as their more general negative affective valence. Therefore, a treatment-seeking group of spider phobic women were treated individually by means of a one-session exposure in vivo along the lines of Öst (1989a). In the counterconditioning condition, tasty food-items were presented during the regular exposure exercises and the participants' favourite music was played.
We used music because of its easy entry in the affective system and its capacity to modify affective responses (e.g. Martin, 1990). In addition, there is already preliminary evidence for the applicability of music in the treatment of animal phobia. That is, using a within subjects design Eifert and colleagues demonstrated in a group of 6 animal phobics that decreases in fear as well as positive changes in the evaluation of the feared animals were greater during exposure sessions (3×25 min) with liked music than in the sessions without music (Eifert, Craill, Carey & O'Connor, 1988). Thus, these results support the idea that liked music can be used in a clinical context to achieve positive evaluative conditioning effects. In a similar vein we expected that the use of tasty food-items during the exposure exercises would act in a way to reduce the spiders' disgusting properties and to change the evaluation of spiders in a positive direction.
The therapist encouraged the participants to eat and drink their favourite items during the exposure exercises and to observe the spider(s) while guiding them across the (unwrapped) food-items, etc. (see procedure section). The counterconditioning exercises were only performed during the final 30 min of the 3 h sessions. This was done because a considerable reduction of fear is a necessary prerequisite for carrying out such exercises successfully and to prevent the intense fear during the earlier phases of the session from reducing the positive valence of the music and the food-items rather than vice versa resulting in counterconditioning in the wrong direction (cf. Eifert et al., 1988). In the control condition, the women continued with the regular exposure exercises during the final 30 min of the session.
Following Baeyens et al., 1989 and Baeyens et al., 1992 we expected that the regular exposure treatment would not alter the affective-evaluative component of spider phobia. In addition, we predicted that counterconditioning would lead to superior treatment results especially with regard to the spiders' valence and disgust evoking status. Finally, we predicted a more general (positive) effect of counterconditioning after one year follow up, as it was thought to prevent the return of phobic complaints.